Method of sweetening hydrocarbon oil



V Patented Aug. 20, 1935 HYDROCARBON OIL poration'of'Delaware Charles F;Teichnia'nn, New York, Ncligassignon any, New York, N. Y., a' cor-i rwing Application January 27;"19325 i i 1 g Serial No. 589,320

I invention relatesgtothe refiningof hydro;

carbomoils and particularly to a process of in+ creasing the reactivityof suspensions of lead compounds in alkaline solutions used forsweetenu5 m hydrocarbon oils; 7 k I Most light mineraloildistillatessuch asigasoline orkerosene contain sulfur compounds whichimpartdisagreeable odors to theoil. It has been common practice toremove these sulfur comm pounds "from the oils by agitating them with analkaline solution of an alkali metalplumbite such as sodium plumbite,prepared by I dissolving lead oxidellinan excess of sodium hydroxide.This treatment pauses :a reaction between the sulfur compounds such asmercaptans and the plumbite solution with the formation of colored leadcom pounds such 'as lead mercaptidesr In orderpto decompose these leadcompounds, it is necessary to add free sulfur, jwhereuponthe lead-ispre- '2 cipitated as the insoluble lead sulfide which-perity of theyproduct resulting from its use, the ex-.

1 ceptionally high cost 'introducesa 'serious' disadvantage. It is knownthat in the. case. offhigh sulfur naphth'as} asmuch as one pound oflitharge per barrel of gasoline. mayfb'e consumed in the V operation 'iI e r r Several new methods of sweetening have been proposed in ordertocircumventthe difiic-ulties ofanj alkali plumbite-sulfur method oftreating; Mostj'of these methods feature a vigorous. direct 40 oxidationof the sulfur compounds by means of oxidizing agents. It has beenioundby the inventor that in the case of certain light hydrocarbonsthese Vmethods 'offdesulfurizingi may result inundesirable reductions incolor stability and decreases theantikncckvalues or the i finishedproducts" due to the factthat the oxidae I 'tion'ca'nnot be limited tothe sulfurfcomp'ounds alonebut extendstoa vigorous actionon' thoseunstable hydrocarbon compounds" which 'by their very nature contributedesirable characteristics to the hydrocarbon products in which they arepresent. f g It has-also been proposed" to agitatelight by drocarbon oildistillates'with a suspension of lead lfide in. a solution: oijicaustic'alkali." In

"or stable highe'molecular' weight {mercar'it order to activate:thesuspension itis; subjected to the actiontof 'air." It maybe"neeessaiyiiua process when treating light hydrocarbon foils on; tai'nin'gextremely stablesul'fu'r com oundsto bleed in 'quantities'ofoxygen oroxygeh containing gases while the hydrocarbon oils'are being agitatedwith the treating solution, The. reaction' which occurs: is" consideredby some to' 'be' a -u a process is ofvalu'e; and fin'dsrea'd cation inthetreatment of straight runfdistillates n and"' sonie cracked petroleumproduc f-With some of the 'naphth'as obtained bici'alnihnidif ficultieshave arisen inits application whieh'dif ficulties are directly-traceabletoijthepresence quiring disproportionately (long, agi tat ion thetreating solutioni Thesta v v these mercaptans is such th'atftl'ieyjremain changed even when contacted with 'thetiati'ng solution and oxygenor oxygen-containing-lgases'.

Such naphthas require at teretreatment'awith a1- kali plumbite andsulfur to make them satis 25 factory for commercial purposes; 'Ili'euse'of" r, indirect contact with the 'oil is extremelyfune desirablesince it reduces the stability of the oil,

' increases substantially the fire hazard "and brings about highevaporationlosses whichin tur'nflini- 30 crease the loadonthe-gasolineabsorption plant.

By the applicationof my inventionifIar'nien 'abled to share intheadvantagesof 'all' of the above mentioned pr cesses 'while avoidingtheir respectivedisadvantages.' A 3 I have discovered'thatwhen" smallquantities of organic or inorganic peroxides are added tof'a suspensionof lead sulfide in an alkaline solution; thehigh-molecular weightmercaptans which" are 'not 'acted upon'by the ordinary leadsulfid'e'jsusj- 40 pensions in caustic solutions; are readilyfattackejdand removed; I h'avelikewise found tha'tthe life of my treating solutionis longer than; any otherpropos'ed to date. The naphthastreatedtherewith are stablefto lightfai' d storage and 45 the'timenecessarydo'r reaction-{is greatlyi q e creasedf' v v n i To explainthextradrdinarir {results' obtained with this treatingsolution, ,Iadvancethefollow ing theoretical explanationtothe'correctness of 50which; I do not 'intend-toilimit "myself; q 1 .When an unsweetenednaphtha is treated with a suspension of lead sulfide insodiumzhydroxide, said treating solution having rbeenactivated prejvia'usl'y by the introduction} of oxygen oroxygen containing gas, it isobserved that the lowmolecular weight mercaptans are readily oxidized todisulfides. .There is also usually a slight discoloration of the naphthawhich can be removed by the introduction of a small quantity ofelementary sulfur. An analysis of the. peroxide content 30f the naphthabefore and after treatment indicates that'the peroxide content has beenmaterially decreased. It is believed that the or: ganic peroxides reactwith the lead sulfides sus-' pended in the sodium hydroxide according tothe.

following reaction:

PbS+4 C +4Naon- 0 +4H2O NflzPbOrl- Thesodiuxn plumbite formed mthis wayis then available for reacting with the high-molecular weightmercaptansin the usual manner.

By increasing the concentration of the organic peroxides to such a valueas to make the available oxygen content equivalent to the sulfurcontent. of the high-molecular weight mercaptans,

it possible to. completely sweeten the naphtha bymea'nsof asuspension'of lead sulfide insodium {The sodium plumbite formed in thismanner is "available for reaction withthestable mercaptans,

reacting with them according to the equation set down heretofore. It isof interest to note that when usingmyprooess, sulfuris necessary inorder to decompose the'lead mercaptides that are formed. v a V .II havenoted that mercaptans react very slowly with peroxides. This explainswhy naphthas containing both these compounds do not become fsweet onstorage due-ftothe decomposition of the niercaptans. However, in thepresence of lead sulfide an alkaline solution the reaction fgoesl veryreadily and is almost" quantitive.- I have also. observed that thesurface of the gran ular lead sulfide used asa starting material in myprocessgradually becomes eroded, eventually losing its solidcharacterand becoming fiocculent. As' a specific exampleof the practice of myinvention I give below the constitution of a treating solution whichmaybe usedfor sweetening a. cracked naphtha containing approximately 0.20%

of high-molecular weight mercaptanswhich do While l 'have shown sodiumhydroxide in'the above composition, it is understood that solutionssubstances which decompose to yield found that inorganic peroxides when.

of alkaline or caustic compounds or mixtures of these may be used in itsstead. Among these may be identified solutions of ammonium hydroxide,potassium carbonate, calcium hydroxide, sodium carbonate, potassiumhydroxide, trisodium phosphate and similar compounds of alkalinereaction.

;'I'he sodium peroxidemay be replaced by equivalent amounts of hydrogenperoxide, barium peroxide, sodium perborate or any such inorganichydrogen peroxide in aqueous solutions.

I Organic peroxides, such as acetic peroxide, benzoyl peroxide,methyl-ethyl ketone peroxide 1 or any organic compound that is apotential source of hydrogen peroxide or nascent oxygen may besubstituted for or used in conjunction with the inorganic peroxides.

My invention readily lends itself to continuous operation, in which casethe hydrocarbon oil to be sweetened is intimately mixed with thesuspension of leadsulfide in alkaline solution to which has beenadded'the correct quantity of the suitable peroxide. After thoroughagitation the mixture is conductedthrough'one or more settling chambers,where the velocity of flow is reduced to such a rate as to allow theseparation of the oil from the treating solution. The separated oil isthen contacted with the proper amount of sulfur to bringaboutthe'decomposition of the lead mercaptidesinto-the correspondingorganic disulfides and lead sulfide. j,

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be .madewithout departing from the spiritand scope method of sweetening hydrocarbon'oils which comprises reactingthe oil with a suspension of lead sulfide in an alkaline solutioncontaining inorganic peroxides.

2. A method of sweetening hydrocarbon oils which comprises reacting theoil with a suspension of lead sulfide in an alkaline solutioncontainingdissolved inorganic peroxides and thenrreacting said oil with elementarysulfur. 3. A method of sweetening hydrocarbon oils which comprisesreacting the oil with a treating suspension consisting of lead sulfide,an aqueous arating the treated oil from the resulting suspensionand thenreacting the treated oil with elementary sulfur. i

5. A method of sweetening hydrocarbonoils which comprises reacting'theoil witha treating suspension consisting of lead sulfide, an aqueousalkaline solution and an" inorganic eroxide, se

arating the treatedoil from thetreating suspension and then reacting thetreate'doil with ele: mentary, sulfur, r w

6. A method of'sweetening hydrocarbon oils whichcomprises reacting theoil with a-treating suspensionconsisting of lead sulfide, an aqueoussolutionof sodiumhydroxide and sodium peroxide, separating the treatedoil from the treating suspension and'then reacting the treated oil withelementary sulfur.v p L I CHARLES F. TEICHMANN.

